Engine Lubrication

ABSTRACT

A trunk piston or cross-head diesel engine having a centrifuge system including a sealing medium is lubricated with a lubricant which, for the cross-head engine, is a system lubricant and which contains 0.04 to 5 mass %, expressed as active ingredient, of a combination of one or more linked aromatic compounds and one or more nitrogen containing ashless disperants, in a mass:mass ratio in the range of 1:3 to 9:1.

FIELD OF THE INVENTION

This invention concerns diesel engine lubrication, more specificallytrunk piston diesel engine lubrication using trunk piston engine oil(‘TPEO’) and system lubrication of crosshead (also referred to astwo-stroke or slow speed) diesel engines.

BACKGROUND OF THE INVENTION

Trunk piston diesel engines are used in marine, power generation andrail traction applications and typically have a rated speed of between300 and 1000 rpm. In trunk piston diesel engines a single lubricantcomposition is used for crankcase and cylinder lubrication. All majormoving parts of the engine, i.e. the main and big end bearings, camshaftand valve gear, are lubricated by a pumped circulation system. Thecylinder liners are lubricated partially by splash lubrication andpartially by oil from the circulation system which finds its way to thecylinder wall through holes in the piston skirt via the connecting rodand gudgeon pin. Crosshead diesel engines, on the other hand, arelubricated using two separate lubricants; the engine cylinders arelubricated using a marine diesel cylinder lubricant (or ‘MDCL’), and theengine crankcase is lubricated using a separate lubricant referred to asa system oil.

Trunk piston diesel engines use a centrifuge system to removecontaminants, such as for example, soot or water, from the lubricatingoil composition. Similar centrifuge systems are used to treat the systemoil of some crosshead marine diesel engines. The centrifuge systemrelies on the use of a sealing medium that is heavier than thelubricating oil composition. The sealing medium is generally water. Whenthe lubricating oil composition passes through the centrifuge system, itcomes into contact with the water. The lubricating oil compositiontherefore needs to be capable of shedding the water and remaining stablein the presence of water. If the lubricating oil composition is unableto shed the water, the water builds up in the lubricating oilcomposition forming an emulsion, which leads to deposits building up inthe centrifuge system and prevents the centrifuge system from workingproperly.

US-A1-2006/0189492 describes certain linked aromatic compounds that actas soot dispersants in lubricating oil compositions. It does not,however, describe their use in trunk piston or crosshead diesel enginelubrication or the need to be capable of shedding water.

SUMMARY OF THE INVENTION

The present invention provides lubrication that improves soot handlingand that is capable of shedding media used in centrifuge systems. Theinvention employs the above-mentioned linked aromatic compounds incombination with nitrogen-containing ashless dispersant in definedratios.

In a first aspect, the invention comprises a method of lubricating atrunk piston diesel engine, or cross-head diesel engine, having acentrifuge system including a sealing medium, the method comprisingoperation of the engine and lubrication of the trunk piston engine orsystem lubrication of the cross-head engine with a lubricating oilcomposition comprising:

-   -   (A) an oil of lubricating viscosity, in a major amount; and    -   (B) 0.04 to 5 mass %, expressed as active ingredient, of the        lubricating oil composition, of a combination of:        -   (B1) at least one linked aromatic compound of the formula:

-   -   -   wherein:        -   each Ar independently represents an aromatic moiety having 0            to 3 substituents selected from the group consisting of            alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, acyloxy,            acyloxyalkyl, aryloxy, aryloxy alkyl, halo and combinations            thereof;        -   each L is independently a linking moiety comprising a            carbon-carbon single bond or a linking group;        -   each Y′ is independently a moiety of the formula            Z(O(CR₂)_(n))_(y)X—, wherein X is selected from the group            consisting of (CR′₂)_(z), O and S; R and R′ are each            independently selected from H, C₁ to C₆ alkyl and aryl;        -   z is 1 to 1 0; n is 0 t 10 when X is (CR′₂)_(z), and 2 to 10            when X s O or S; y is 1 to 30; Z is H, an acyl group, an            alkyl group or an aryl group;        -   each a is independently 0 to 3, with the proviso that at            least one Ar moiety bears at least one group Y′ in which Z            is not H; and        -   m is 1 to 100; and        -   (B2) at least one nitrogen-containing dispersant, where the            mass:mass ratio of (B1) to (B2) is in the range from 1:3 to            9:1, preferably in the range from 1:1 to 6:1, such as 3:1 to            6:1.

In a second aspect, the invention comprises a method of enhancing thewater-shedding properties, as measured by a centrifuge water sheddingtest, of a lubricating oil composition in the lubrication of a trunkpiston engine, or the system lubrication of cross-head diesel engine,having a centrifuge system including a sealing medium, by employing alubricating oil composition as defined in the first aspect of theinvention when compared with a corresponding lubricating oil compositionwhere (B) contains only (B2).

In a third aspect, the invention comprises a trunk piston or cross-headdiesel engine lubricating oil composition having a total base number ofat least 15, such as at least 20, mg KOH/g, as determined by ASTM D2896,comprising:

-   -   (A) at least 40 mass % of an oil lubricating viscosity; and    -   (B) 0.04 to 5 mass %, expressed as active ingredient, of the        lubricating oil composition, of a combination of:        -   (B1) at least one linked aromatic compound of the formula:

-   -   -   wherein:        -   each Ar independently represents an aromatic moiety having 0            to 3 substituents selected from the group consisting of            alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, acyloxy,            acyloxyalkyl, aryloxy, aryloxy alkyl, halo and combinations            thereof;        -   each L is independently a linking moiety comprising a            carbon-carbon single bond or a linking group;        -   each Y′ is independently a moiety of the formula            Z(O(CR₂)_(n))_(y)X—, wherein X is selected from the group            consisting of (CR′₂)_(z), O and S; R and R′ are each            independently selected from H, C₁ to C₆ alkyl and aryl;        -   z is 1 to 10; n is 0 to 10 when X is (CR′₂)_(z), and 2 to 10            when X is O or S; y is 1 to 30; Z is H, an acyl group, an            alkyl group or an aryl group;        -   each a is independently 0 to 3, with the proviso that at            least one Ar moiety bears at least one group Y′ in which Z            is not H; and        -   m is 1 to 100; and        -   (B2) at least one nitrogen-containing dispersant, where the            mass:mass ratio of (B I) to (B2) is in the range from 1:3 to            9:1, preferably in the range from 1:1 to 6:1, such as 3:1 to            6:1.

In this specification, the following words and expressions, if and whenused, have the meanings ascribed below:

-   -   “active ingredient” or “(a.i.)” refers to additive material that        is not diluent or solvent;    -   “comprising” or any cognate word specifies the presence of        stated features, steps, or integers or components, but does not        preclude the presence or addition of one or more other features,        steps, integers, components or groups thereof; the expressions        “consists of” or “consists essentially of” or cognates may be        embraced within “comprises” or cognates, wherein “consists        essentially of” permits inclusion of substances not materially        affecting the characteristics of the composition to which it        applies;    -   “major amount” means in excess of 50 mass % of a composition;    -   “minor amount” means less than 50 mass % of a composition;    -   “TBN” means total base number as measured by ASTM D2896.        Furthermore in this specification:    -   “phosphorus content” is as measured by ASTM D5185;    -   “sulphated ash content” is as measured by ASTM D874;    -   “sulphur content” is as measured by ASTM D2622;    -   “KV100” means kinematic viscosity at 100° C. as measured by ASTM        D445.

Also, it will be understood that various components used, essential aswell as optimal and customary, may react under conditions offormulation, storage or use and that the invention also provides theproduct obtainable or obtained as a result of any such reaction.

Further, it is understood that any upper and lower quantity, rage andratio limits set forth herein may be independently combined.

DETAILED DESCRIPTION OF THE INVENTION

The features of the invention relating, where appropriate, to each andall aspects of the invention, will now be described in more detail asfollows:

(B1) Linked Aromatic Compound

US 2006/0189492 A1 describes these compounds which can be prepared fromcompounds of formula (I) below.

wherein each Ar independently represents an aromatic moiety having 0 to3 substituents selected from the group consisting of alkyl, alkoxy,alkoxyalkyl, hydroxy, hydroxyalkyl, halo and combinations thereof; eachL is independently a linking moiety comprising a carbon-carbon singlebond or a linking group; each Y is independently a moiety of the formulaH(O(CR₂)_(n))_(y)X—, wherein X is selected from the group consisting of(CR′₂)_(z), O and S; R and R′ are each independently selected from H, C₁to C₆ alkyl and aryl; z is 1 to 10; n is 0 to 10 when X is (CR′₂)_(z),and 2 to 10 when X is O or S; and y is 1 to 30; each a is independently0 to 3, with the proviso that at least one Ar moiety bears at least onegroup Y; and m is 1 to 100.

Aromatic moieties Ar of Formula (I) can be a mononuclear carbocyclicmoiety (phenyl) or a polynuclear carbocyclic moiety. Polynuclearcarbocyclic moieties may comprise two or more fused rings, each ringhaving 4 to 10 carbon atoms (e.g., naphthalene) or may be linkedmononuclear aromatic moieties, such as biphenyl, or may comprise linked,fused rings (e.g., binaphthyl). Examples of suitable polynuclearcarbocyclic aromatic moieties include naphthalene, anthracene,phenanthrene, cycopentenophenanthrene, benzanthracene, dibenzanthracene,chrysene, pyrene, benzpyrene and coronene and dimer, trimer and higherpolymers thereof. Ar can also represent a mono- or polynuclearheterocyclic moiety. Heterocyclic moieties Ar include those comprisingone or more rings each containing 4 to 10 atoms, including one or morehetero atoms selected from N, O and S. Examples of suitable monocylicheterocyclic aromatic moieties include pyrrole, furan, thiophene,imidazole, oxazole, thiazole, pyrazole, pyridine, pyrimidine and purine.Suitable polynuclear heterocyclic moieties Ar include, for example,quinoline, isoquinoline, carbazole, dipyridyl, cinnoline, phthalazine,quinazoline, quinoxaline and phenanthroline. Each aromatic moiety (Ar)may be independently selected such that all moieties Ar are the same ordifferent. Polycyclic carbocyclic aromatic moieties are preferred. Mostpreferred are compounds of Formula I wherein each Ar is naphthalene.Each aromatic moiety Ar may independently be unsubstituted orsubstituted with 1 to 3 substituents selected from alkyl, alkoxyalkoxyalkyl, hydroxyl, hydroxyalkyl, halo, and combinations thereof.Preferably, each Ar is unsubstituted (except for group(s) Y and terminalgroups).

Each linking group (L) may be the same or different, and can be a carbonto carbon single bond between the carbon atoms of adjacent moieties Ar,or a linking group. Suitable linking groups include alkylene linkages,ether linkages, diacyl linkages, ether-acyl linkages, amino linkages,amido linkages, carbamido linkages, urethane linkages, and sulfurlinkage. Preferred linking groups are alkylene linkages such as—CH₃CHC(CH₃)₂—, or C(CH₃)₂—; diacyl linkages such as —COCO— or—CO(CH₂)₄CO—; and sulfur linkages, such as —S₁— or —S_(x)—. Morepreferred linking groups are alkylene linkages, most preferably —CH₂—.

Preferably, Ar of Formula (I) represents naphthalene, and morepreferably, Ar is derived from 2-(2-naphthyloxy)-ethanol. Preferably,each Ar is derived from 2-(2-naphthyloxy)-ethanol, and m is 2 to 25.Preferably, Y of Formula (I) is the group H(O(CR₂)₂)_(y)O—, wherein y is1 to 6. More preferably, Ar is naphthalene, Y is HOCH₂C₂O— and L is—CH₂—.

Methods for forming compounds of Formula (I) should be apparent to thoseskilled in the art. A hydroxyl aromatic compound, such as naphthol canbe reacted with an alkylene carbonate (e.g., ethylene carbonate) toprovide a compound of the formula AR—(Y)_(a). Preferably, the hydroxylaromatic compound and alkylene carbonate are reacted in the presence ofa base catalyst, such as aqueous sodium hydroxide, and at a temperatureof from 25 to 300, preferably from 50 to 200° C. During the reaction,water may be removed from the reaction mixture by azeotropicdistillation or other conventional means. If separation of the resultingintermediate product is desired, upon completion of the reaction(indicated by the cessation of CO₂ evolution), the reaction product canbe collected, and cooled to solidify. Alternatively, a hydroxyl aromaticcompound, such as naphthol, can be reacted with an epoxide, such asethylene oxide, propylene oxide, butylenes oxide or styrene oxide, undersimilar conditions to incorporate one or more oxy-alkylene groups.

To form a compound of Formula (I), the resulting intermediate compoundAr—(Y)_(a) may be further reacted with a polyhalogenated (preferablydihalogenated) hydrocarbon (e.g., 1-4-dichlorobutane,2,2-dichloropropane, etc.), or a di- or poly-olefin (e.g., butadiene,isoprene, divinylbenzene, 1,4-hexadiene, 1,5-hexadiene, etc.) to yield acompound of Formula (I) having an alkylene linking groups. Reaction ofmoieties Ar—(Y)_(a) and a ketone or aldehyde (e.g., formaldehyde,acetone, benzophenone, acetophenone, etc.) provides an alkylene-linkedcompound. An acyl-linked compound can be formed by reacting moietiesAr—(Y)_(a) with a diacid or anhydride (e.g., oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, succinic anhydride, etc.).Sulfide, polysulfide, sulfinyl and sulfonyl linkages may be provided byreaction of the moieties Ar—(Y)_(a) with a suitable difunctionalsulfurizing agent (e.g., sulfur monochloride, sulfur dichloride, thionylchloride (SOCl₂), sulfuryl chloride (SO₂Cl₂), etc.). To provide acompound of Formula (I) with an alkylene ether linkage, moietiesAr—(Y)_(a) can be reacted with a divinylether. Compounds of Formula (I),wherein L is a direct carbon to carbon link, may be formed via oxidativecoupling polymerization using a mixture of aluminum chloride and cuprouschloride, as described, for example, by P. Kovacic, et al., J. PolymerScience: Polymer Chem. Ed., 21, 457 (1983). Alternatively, suchcompounds may be formed by reacting moieties Ar—(Y)_(a) and an alkalimetal as described, for example, in “Catalytic Benzene Coupling onCaesium/Nanoporous Carbon Catalysts”, M. G. Stevens, K. M. Sellers, S.Subramoney and H. C. Foley, Chemical Communications, 2679-2680 (1988).

To form the preferred compounds of Formula (I), having an alkylenelinking group, more preferably a methylene linking group, base remainingin the Ar—(Y)_(a) reaction mixture can be neutralized with acid,preferably with an excess of acid (e.g., a sulfonic acid) and reactedwith an aldehyde, preferably formaldehyde, and preferably in thepresence of residual acid, to provide an alkylene, preferably methylenebridged compound of Formula (I). The degree of polymerization of thecompounds of Formula I range from 2 to 101 (corresponding to a value ofm of from 1 to 100), preferably from 2 to 50, most preferably from 2 to25.

The compounds of formula (II) can be formed by reacting a compound offormula (I) with at least one of an acylating agent, an alkylating agentand an arylating agent, and are represented by the formula:

wherein each Y′ is independently a moiety of the formulaZ(O(CR₂)_(n))_(y)X—; Z is an acyl group, an alkyl group or an aryl groupor H, and Ar, L, X, R, z, n and y are the same as defined in Formula(I), with the proviso that, at least one Ar moiety bears at least onesubstituent group Y′ in which Z is not H; and m is 1 to 100.

Suitable acylating agents include hydrocarbyl carbonic acid, hydrocarbylcarbonic acid halides, hydrocarbyl sulfonic acid and hydrocarbylsulfonic acid halides, hydrocarbyl phosphoric acid and hydrocarbylphosphoric halides, hydrocarbyl isocyanates and hydrocarbyl succinicacylating agents. Preferred acylating agents are C₈ and higherhydrocarbyl isocyanates, such as dodecyl isocyanate and hexadodecylisocyanate and C₈ or higher hydrocarbyl acylating agents, morepreferably polybutenyl succinic acylating agents such as polybutenyl, orpolyisobutenyl succinic anhydride (PIBSA). Preferably the hydrocarbylsuccinic acylating agent will have a number average molecular weight ( M_(n)) of from 100 to 5000, preferably from 200 to 3000, more preferablyfrom 450 to 2500. Preferred hydrocarbyl isocyanate acylating agent willhave a number average molecular weight ( M _(n)) of from 100 to 5000,preferably from 200 to 3000, more preferably from 200 to 2000.

Acylating agents can be prepared by conventional methods known to thoseskilled in the art, such as chlorine-assisted, thermal and radicalgrafting methods. The acylating agents can be mono- or polyfunctional.Preferably, the acylating agents have a functionality of less than 1.3.Acylating agents are used in the manufacture of dispersants, and a moredetailed description of methods for forming acylating agents isdescribed in the description of suitable dispersants, presented infra.

Suitable alkylating agents include C₈ to C₃₀ alkane alcohols, preferablyC₈ to C₁₈ alkane alcohols. Suitable arylating agents include C₈ to C₃₀,preferably C₈ to C₁₈ alkane-substituted aryl mono- or polyhydroxide.

Molar amounts of the compound of Formula (I) and the acylating,alkylating and/or arylating agent can be adjusted such that all, or onlya portion, such as 25% or more, 50% or more or 75% or more of groups Yare converted to groups Y′. In the case where the compound of Formula(I) has hydroxy and/or alkyl hydroxy substituents, and such compoundsare reacted with an acylating group, it is possible that all or aportion of such hydroxy and/or alkylhydroxy substituents will beconverted to acyloxy or acyloxy alkyl groups. In the case where thecompound of Formula (I) has hydroxy and/or alkyl hydroxy substituents,and such compounds are reacted with an arylating group, it is possiblethat all or a portion of such hydroxy and/or alkylhydroxy substituentswill be converted to aryloxy or aryloxy alkyl groups. Therefore,compounds of Formula (II) substituted with acyloxy, acyloxy alkyl,aryloxy and/or aryloxy alkyl groups are considered within the scope ofthe present invention. A salt form of compounds of Formula (II) in whichZ is an acylating group, which salts result from neutralization withbase (as may occur, for example, due to interaction with a metaldetergent, either in an additive package or a formulated lubricant), isalso considered to be within the scope of the invention.

Compounds of Formula (II) can be derived from the precursors of Formula(I) by reacting the precursors of Formula (I) with the acylating agent,preferably in the presence of a liquid acid catalyst, such as sulfonicacid, e.g., dodecyl benzene sulfonic acid, paratoluene sulfonic acid orpolyphosphoric acid or a solid acid catalyst such as Amberlyst-15,Amberlyst-36, zeolites, mineral acid clay or tungsten polyphosphoricacid; at a temperature of from about 0 to 300, preferably from 50 to250° C. Under the above conditions, the preferred polybutenyl succinicacylating agents can form diesters, acid esters or lactone esters withthe compound of Formula (I).

Compounds of Formula (II) can be derived from the precursors of Formula(I) by reacting the precursors of Formula (I) with the alkylating agentor arylating agent, preferably in the presence of triphenylphosphine anddiethyl azodicarboxylate (DEAD), a liquid acid catalyst, such assulfonic acid, e.g., dodecyl benzene sulfonic acid, paratoluene sulfonicacid or polyphosphoric acid or a solid acid catalyst such asAmberlyst-15, Amberlyst-36, zeolites, mineral acid clay or tungstenpolyphosphoric acid; at a temperature of from 0 to 300, preferably from50 to 250° C.

(B2) Ashless Dispersant

Ashless dispersants useful in the compositions of the present inventioncomprise an oil-soluble polymeric long chain backbone having functionalgroups capable of associating with particles to be dispersed. Typically,such dispersants comprise amine, alcohol, amide or ester polar moietiesattached to the polymer backbone, often via a bridging group. Theashless dispersant may be, for example, selected from oil-soluble salts,esters, amino-esters, amides, imides and oxazolines of long chainhydrocarbon-substituted mono- and polycarboxylic acids or anhydridesthereof; thiocarboxylate derivatives of long chain hydrocarbons; longchain aliphatic hydrocarbons having polyamine moieties attached directlythereto; and Mannich condensation products formed by condensing a longchain substituted phenol with formaldehyde and polyalkylene polyamine.

Preferably, the ashless dispersant is a “high molecular weight”dispersant having a number average molecular weight ( M _(n)) greaterthan or equal to 4,000, such as between 4,000 and 20,000. The precisemolecular weight ranges will depend on the type of polymer used to formthe dispersant, the number of functional groups present, and the type ofpolar functional group employed. For example, for apolyisobutylene-derivatized dispersant, a high molecular weightdispersant is one formed with a polymer backbone having a number averagemolecular weight of from 1680 to 5600. Typical commercially-availablepolyisobutylene-based dispersants contain polyisobutylene polymershaving a number average molecular weight ranging from 900 to 2300,functionalized by maleic anhydride (MW98), and derivatized withpolyamines having a molecular weight of from 100 to 350. Polymers oflower molecular weight may also be used to form high molecular weightdispersants by incorporating multiple polymer chains into thedispersant, which can be accomplished using methods that are known inthe art.

Polymer molecular weight, specifically number average molecular weight (M _(n)), can be determined by various known techniques. One convenientmethod is gel permeation chromatography (GPC), which additionallyprovides molecular weight distribution information (see W. W. Yau, J. J.Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”,John Wiley and Sons, New York. 1979). If the molecular weight of anamine-containing dispersant (e.g., PIBSA-polyamine or PIBSA-PAM) isbeing determined, the presence of the amine may cause the dispersant tobe adsorbed by the column, leading to an inaccurate molecular weightdetermination. Persons familiar with the operation of GPC equipmentunderstand that this problem may be eliminated by using a mixed solventsystem, such as tetrahydrofuran (THF) mixed with a minor amount ofpyridine, as opposed to pure THF. The problem may also be addressed bycapping the amine with acetic anhydride and correcting the molecularweight based on the number of capping groups. Another useful method fordetermining molecular weight, particularly for lower molecular weightpolymers, is vapor pressure osmometry (see, e.g., ASTM D3592).

The degree of polymerization D_(p) of a polymer is:

$D_{p} = {\sum\limits_{i}\; \frac{{Mn} \times {{mol}.\; \%}\mspace{14mu} {monomer}\mspace{14mu} i}{100 \times {{mol}.\mspace{11mu} {wt}}\mspace{14mu} {monomer}\mspace{14mu} i}}$

and thus for the copolymers of two monomers D_(P) may be calculated asfollows:

$D_{p} = {\frac{{Mn} \times {{mol}.\; \%}\mspace{14mu} {monomer}\mspace{14mu} 1}{100 \times {{mol}.\mspace{11mu} {wt}}\mspace{14mu} {monomer}\mspace{14mu} 1} + \frac{{Mn} \times {{mol}.\; \%}\mspace{14mu} {monomer}\mspace{14mu} 2}{100 \times {{mol}.\mspace{11mu} {wt}}\mspace{14mu} {monomer}\mspace{14mu} 2}}$

Preferably, the degree of polymerization for the polymer backbones usedin the invention is at least 30, typically from 30 to 165, morepreferably 35 to 100.

The preferred hydrocarbons or polymers employed in this inventioninclude homopolymers, interpolymers or lower molecular weighthydrocarbons. One family of useful polymers comprise polymers ofethylene and/or at least one C₃ to C₂₈ alpha-olefin having the formulaH₂C═CHR¹, wherein R¹ is straight or branched chain alkyl radicalcomprising 1 to 26 carbon atoms and wherein the polymer containscarbon-to-carbon unsaturation, preferably a high degree of terminalethenylidene unsaturation. One preferred class of such polymers employedin this invention comprise interpolymers of ethylene and at least onealpha-olefin of the above formula, wherein R¹ is alkyl of from 1 to 18carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms,and more preferably still of from 1 to 2 carbon atoms. Therefore, usefulalpha-olefin monomers and comonomers include, for example, propylene,butene-1, hexene-1, octene-1,4-methylpentene-1, decene-1, dodecene-1,tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1,octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures ofpropylene and butene-1, and the like). Exemplary of such polymers arepropylene homopolymers, butene-1 homopolymers, propylene-butenecopolymers, ethylene-propylene copolymers, ethylene-butene-1 copolymersand the like, wherein the polymer contains at least some terminal and/orinternal unsaturation. Preferred polymers are unsaturated copolymers ofethylene and propylene and ethylene and butene-1. The interpolymers ofthis invention may contain a minor amount, e.g. 0.5 to 5 mole % of a C₄to C₁₈ non-conjugated diolefin comonomer. However, it is preferred thatthe polymers of this invention comprise only alpha-olefin homopolymers,interpolymers of alpha-olefin comonomers and interpolymers of ethyleneand alpha-olefin comonomers. The molar ethylene content of the polymersemployed in this invention is preferably in the range of 20 to 80, morepreferably 30 to 70%. When propylene and/or butene-1 are employed ascomonomer(s) with ethylene, the ethylene content of such copolymers ismost preferably between 45 and 65%, although higher or lower ethylenecontents may be present.

These polymers may be prepared by polymerizing alpha-olefin monomer, ormixtures of alpha-olefin monomers, or mixtures comprising ethylene andat least one C₃ to C₂₈ alpha-olefin monomer, in the presence of acatalyst system comprising at least one metallocene (e.g., acyclopentadienyl-transition metal compound) and an alumoxane compound.Using this process, a polymer in which 95% or more of the polymer chainspossess terminal ethenylidene-type unsaturation can be provided. Thepercentage of polymer chains exhibiting terminal ethenylideneunsaturation may be determined by FTIR spectroscopic analysis,titration, or C¹³ NMR. Interpolymers of this latter type may becharacterized by the formula POLY-C(R¹)═CH₂ wherein R¹ is C₁ to C₂₆alkyl, preferably C₁ to C₁₈ alkyl, more preferably C₁ to C₈ alkyl, andmost preferably C₁ to C₂ alkyl, (e.g., methyl or ethyl) and wherein POLYrepresents the polymer chain. The chain length of the R¹ alkyl groupwill vary depending on the comonomer(s) selected for use in thepolymerization. A minor amount of the polymer chains can containterminal ethenyl, i.e., vinyl, unsaturation, ice, POLY-CH═CH₂, and aportion of the polymers can contain internal monounsaturation, e.g.POLY-CH═CH(R¹), wherein R¹ is as defined above. These terminallyunsaturated interpolymers may be prepared by known metallocene chemistryand may also be prepared as described in U.S. Pat. Nos. 5,498,809;5,663,130; 5,705,577; 5,814,715; 6,022,929 and 6,030,930.

Another useful class of polymers comprises polymers prepared by cationicpolymerization of isobutene, styrene, and the like. Common polymers fromthis class include polyisobutenes obtained by polymerization of a C₄refinery stream having a butene content of 35 to 75% by wt., and anisobutene content of 30 to 60% by wt., in the presence of a Lewis acidcatalyst, such as aluminum trichloride or boron trifluoride. A preferredsource of monomer for making poly-n-butenes is petroleum feed streamssuch as Raffinate II. These feedstocks are disclosed in the art such asin U.S. Pat. No. 4,952,739. Polyisobutylene is a most preferred backboneof the present invention because it is readily available by cationicpolymerization from butene streams (e.g., using AlCl₃ or BF₃ catalysts).Such polyisobutylenes generally contain residual unsaturation in amountsof one ethylenic double bond per polymer chain, positioned along thechain.

As noted above, the polyisobutylene polymers employed are generallybased on a hydrocarbon chain of from 900 to 2,300. Methods for makingpolyisobutylene are known. Polyisobutylene can be functionalized byhalogenation (e.g. chlorination), the thermal “ene” reaction, or by feeradical grafting using a catalyst (e.g. peroxide), as described below.

Processes for reacting polymeric hydrocarbons with unsaturatedcarboxylic acids, anhydrides or esters and the preparation ofderivatives from such compounds are disclosed in U.S. Pat. Nos.3,087,936; 3,172,892; 3,215,707; 3,231,587; 3,272,746; 3,275,554;3,381,022; 3,442,808; 3,565,804; 3,912,764; 4,110,349; 4,234,435; andGB-A-1,440,219. The polymer or hydrocarbon may be functionalized, forexample, with carboxylic acid producing moieties (preferably acid oranhydride) by reacting the polymer or hydrocarbon under conditions thatresult in the addition of functional moieties or agents, i.e., acid,anhydride, ester moieties, etc., onto the polymer or hydrocarbon chainsprimarily at sites of carbon-to-carbon unsaturation (also referred to asethylenic or olefinic unsaturation) using the halogen assistedfunctionalization (e.g. chlorination) process or the thermal “ene”reaction.

When using the free radical grafting process employing a catalyst (e.g.peroxide), the functionalization is randomly effected along the polymerchain. Selective functionalization can be accomplished by halogenating,e.g., chlorinating or brominating the unsaturated α-olefin polymer to 1to 8, preferably 3 to 7 wt. % chlorine, or bromine, based on the weightof polymer or hydrocarbon, by passing the chlorine or bromine throughthe polymer at a temperature of 60 to 250, preferably 110 to 160, e.g.,120 to 140° C. for 0.5 to 10, preferably 1 to 7, hours. The halogenatedpolymer or hydrocarbon (hereinafter backbones) can then be reacted withsufficient monounsaturated reactant capable of adding functionalmoieties to the backbone, e.g., monounsaturated carboxylic reactant, at100 to 250, usually 180 to 235° C., for 0.5 to 10, e.g., 3 to 8, hours,such that the product obtained will contain the desired number of molesof the monounsaturated carboxylic reactant per mole of the halogenatedbackbones. Alternatively, the backbone and the monounsaturatedcarboxylic reactant can be mixed and heated while adding chlorine to thehot material.

The hydrocarbon or polymer backbone can be functionalized, e.g., withcarboxylic acid producing moieties (preferably acid or anhydridemoieties) selectively at sites of carbon-to-carbon unsaturation on thepolymer or hydrocarbon chains, or randomly along chains using the threeprocesses mentioned above, or combinations thereof, in any sequence.

The preferred monounsaturated reactants that are used to functionalizethe backbone comprise mono- and dicarboxylic acid material, i.e., acid,anhydride, or acid ester material, including (i) monounsaturated C₄ toC₁₀ dicarboxylic acid wherein (a) the carboxyl groups are vicinyl,(i.e., located on adjacent carbon atoms) and (b) at least one,preferably both, of said adjacent carbon atoms are part of said monounsaturation; (ii) derivatives of (i) such as anhydrides or C₁ to C₅alcohol derived mono- or diesters of (i); (iii) monounsaturated C₃ toC₁₀ monocarboxylic acid wherein the carbon-carbon double bond isconjugated with the carboxy group, i.e., of the structure —C═C—CO—; and(iv) derivatives of (iii) such as C₁ to C₅ alcohol derived mono- ordiesters of (iii). Mixtures of monounsaturated carboxylic materials(i)-(iv) also may be used. Upon reaction with the backbone, themonounsaturation of the monounsaturated carboxylic reactant becomessaturated. Thus, for example, maleic anhydride becomesbackbone-substituted succinic anhydride, and acrylic acid becomesbackbone-substituted propionic acid. Exemplary of such monounsaturatedcarboxylic reactants are fumaric acid, itaconic acid, maleic acid,maleic anhydride, chloromaleic acid, chloromaleic anhydride, acrylicacid, methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl(e.g., C₁ to C₄ alkyl) acid esters of the foregoing, e.g., methylmaleate, ethyl fumarate, and methyl fumarate. The monounsaturatedcarboxylic reactant, preferably maleic anhydride, typically will be usedin an amount ranging from 0.01 to 20, preferably 0.5 to 10 wt. %, basedon the weight of the polymer or hydrocarbon.

While chlorination normally helps increase the reactivity of startingolefin polymers with monounsaturated functionalizing reactant, it is notnecessary with the polymers or hydrocarbons contemplated for use in thepresent invention, particularly those preferred polymers or hydrocarbonswhich possess a high terminal bond content and reactivity. Preferably,therefore, the backbone and the monounsaturated functionality reactant,e.g., carboxylic reactant, are contacted at elevated temperature tocause an initial thermal “ene” reaction to take place. Ene reactions areknown.

The hydrocarbon or polymer backbone can be functionalized by randomattachment of functional moieties along the polymer chains by a varietyof methods. For example, the polymer, in solution or in solid form, maybe grafted with the monounsaturated carboxylic reactant, as describedabove, in the presence of a free-radical initiator. When performed insolution, the grafting takes place at an elevated temperature in therange of 100 to 260, preferably 120 to 240° C. Preferably, free-radicalinitiated grafting is accomplished in a mineral lubricating oil solutioncontaining, for example, 1 to 50, preferably 5 to 30 wt. % polymer basedon the initial total oil solution.

The free-radical initiators that may be used are peroxides,hydroperoxides, and azo compounds, preferably those that have a boilingpoint greater than 100° C. and decompose thermally within the graftingtemperature range to provide free-radicals. Representative of thesefree-radical initiators are azobutyronitrile, bis-tertiary-butylperoxide and dicumene peroxide. The initiator, when used, typically isused in an amount of between 0.005 and 1% by weight based on the weightof the reaction mixture solution. Typically, the aforesaidmonounsaturated carboxylic reactant material and free-radical initiatorare used in a weight ratio range of from 1.0:1 to 30:1, preferably 3:1to 6:1. The grafting is preferably carried out in an inert atmosphere,such as under nitrogen blanketing. The resulting grafted polymer ischaracterized by having carboxylic acid (or ester or anhydride) moietiesrandomly attached along the polymer chains, it being understood, ofcourse, that some of the polymer chains remain ungrafted. The freeradical grafting described above can be used for the other polymers andhydrocarbons of the present invention.

The functionalized oil-soluble polymeric hydrocarbon backbone may thenbe further derivatized with a nucleophilic reactant, such as an amine,amino-alcohol, alcohol, metal compound, or mixture thereof, to form acorresponding derivative. Useful amine compounds for derivatizingfunctionalized polymers comprise at least one amine and can comprise oneor more additional amine or other reactive or polar groups. These aminesmay be hydrocarbyl amines or may be predominantly hydrocarbyl amines inwhich the hydrocarbyl group includes other groups, e.g., hydroxy groups,alkoxy groups, amide groups, nitriles, imidazoline groups, and the like.Particularly useful amine compounds include mono- and polyamines, e.g.,polyalkene and polyoxyalkylene polyamines of 2 to 60, such as 2 to 40(e.g., 3 to 20), total carbon atoms having 1 to 12, such as 3 to 12,preferably 3 to 9, nitrogen atoms per molecule. Mixtures of aminecompounds may advantageously be used, such as those prepared by reactionof alkylene dihalide with ammonia. Preferred amines are aliphaticsaturated amines, including, for example, 1,2-diaminoethane;1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane; polyethyleneamines such as diethylene triamine; triethylene tetramine; tetraethylenepentamine; and polypropyleneamines such as 1,2-propylene diamine; anddi-(1,2-propylene)triamine.

Other useful amine compounds include: alicyclic diamines such as1,4-di(aminomethyl)cyclohexane and heterocyclic nitrogen compounds suchas imidazolines. Another useful class of amines is the polyamido andrelated amido-amines as disclosed in U.S. Pat. Nos. 4,857,217;4,956,107; 4,963,275; and 5,229,022. Also usable istris(hydroxymethyl)amino methane (TAM) as described in U.S. Pat. Nos.4,102,798; 4,113,639; 4,116,876; and UK 989,409. Dendrimers, star-likeamines, and comb-structured amines may also be used. Similarly, one mayuse condensed amines, as described in U.S. Pat. No. 5,053,152. Thefunctionalized polymer is reacted with the amine compound usingconventional techniques as described, for example in U.S. Pat. Nos.4,234,435 and 5,229,022, as well as in EP-A-208,560.

The functionalized, oil-soluble polymeric hydrocarbon backbones may alsobe derivatized with hydroxy compounds such as monohydric and polyhydricalcohols, or with aromatic compounds such as phenols and naphthols.Preferred polyhydric alcohols include alkylene glycols in which thealkylene radical contains from 2 to 8 carbon atoms. Other usefulpolyhydric alcohols include glycerol, mono-oleate of glycerol,monostearate of glycerol, monomethyl ether of glycerol, pentaerythritol,dipentaerythritol, and mixtures thereof. An ester dispersant may also bederived from unsaturated alcohols, such as allyl alcohol, cinnamylalcohol, propargyl alcohol, 1-cyclohexene-3-ol, and oleyl alcohol. Stillother classes of alcohols capable of yielding ashless dispersantscomprise ether-alcohols, including oxy-alkylene and oxy-arylene. Suchether-alcohols are exemplified by ether-alcohols having up to 150oxy-alkylene radicals in which the alkylene radical contains from 1 to 8carbon atoms. The ester dispersants may be di-esters of succinic acidsor acid-esters, i.e., partially esterified succinic acids, as well aspartially esterified polyhydric alcohols or phenols, i.e., esters havingfree alcohols or phenolic hydroxy radicals. An ester dispersant may beprepared by any one of several known methods as described, for example,in U.S. Pat. No. 3,381,022.

Preferred groups of dispersant include polyamine-derivatized polyα-olefin, dispersants, particularly ethylene/butene alpha-olefin andpolyisobutylene-based dispersants. Particularly preferred are ashlessdispersants derived from polyisobutylene substituted with succinicanhydride groups and reacted with polyethylene amines, e.g.,polyethylene diamine, tetraethylene pentamine; or a polyoxyalkylenepolyamine, e.g., polyoxypropylene diamine, trimethylolaminomethane; ahydroxy compound, e.g., pentaerythritol; and combinations thereof. Oneparticularly preferred dispersant combination is a combination of (A)polyisobutylene substituted with succinic anhydride groups and reactedwith (B) a hydroxy compound, e.g., pentaerythritol; (C) apolyoxyalkylene polyamine, e.g., polyoxypropylene diamine, or (D) apolyalkylene diamine, e.g., polyethylene diamine and tetraethylenepentamine using 0.3 to 2 moles of (B), (C) and/or (D) per mole of (A).Another preferred dispersant combination comprises a combination of (A)polyisobutenyl succinic anhydride with (B) a polyalkylene polyamine,e.g., tetraethylene pentamine, and (C) a polyhydric alcohol orpolyhydroxy-substituted aliphatic primary amine, e.g., pentaerythritolor trismethylolaminomethane, as described in U.S. Pat. No. 3,632,511.

Another class of ashless dispersants comprises Mannich base condensationproducts. Generally, these products are prepared by condensing about onemole of an alkyl-substituted mono- or polyhydroxy benzene with 1 to 2.5moles of carbonyl compound(s) (e.g., formaldehyde and paraformaldehyde)and 0.5 to 2 moles of polyalkylene polyamine, as disclosed, for example,in U.S. Pat. No. 3,442,808. Such Mannich base condensation products mayinclude a polymer product of a metallocene catalyzed polymerization as asubstituent on the benzene group, or may be reacted with a compoundcontaining such a polymer substituted on a succinic anhydride in amanner similar to that described in U.S. Pat. No. 3,442,808. Examples offunctionalized and/or derivatized olefin polymers synthesized usingmetallocene catalyst systems are described in the publicationsidentified supra.

The dispersant can be further post treated by a variety of conventionalpost treatments such as boration, as generally taught in U.S. Pat. Nos.3,087,936 and 3,254,025. Boration of the dispersant is readilyaccomplished by treating an acyl nitrogen-containing dispersant with aboron compound such as boron oxide, boron halide boron acids, and estersof boron acids, in an amount sufficient to provide from 0.1 to 20 atomicproportions of boron for each mole of acylated nitrogen composition.Useful dispersants contain from 0.05 to 2.0, e.g., from 0.05 to 0.7,mass % boron. The boron, which appears in the product as dehydratedboric acid polymers (primarily (HBO₂)₃), is believed to attach to thedispersant imides and diimides as amine salts, e.g., the metaborate saltof the diimide. Boration can be carried out by adding from 0.5 to 4,e.g., from 1 to 3 mass % (based on the mass of acyl nitrogen compound)of a boron compound, preferably boric acid, usually as a slurry, to theacyl nitrogen compound and heating with stirring at from 135 to 190,e.g., 140 to 170° C., for from 1 to 5 hours, followed by nitrogenstripping. Alternatively, the boron treatment can be conducted by addingboric acid to a hot reaction mixture of the dicarboxylic acid materialand amine, while removing water. Other post-reaction processes commonlyknown in the art can also be applied.

The dispersant may also be further post treated by reaction with aso-called “capping agent”. Conventionally, nitrogen-containingdispersants have been “capped” to reduce the adverse effect suchdispersants have on the fluoroelastomer engine seals. Numerous cappingagents and methods are known. Of the known “capping agents”, those thatconvert basic dispersant amino groups to non-basic moieties (e.g., amidoor imido groups) are most suitable. The reaction of anitrogen-containing dispersant and alkyl acetoacetate (e.g., ethylacetoacetate (EAA)) is described, for example, in U.S. Pat. Nos.4,839,071; 4,839,072 and 4,579,675. The reaction of anitrogen-containing dispersant and formic acid is described, forexample, in U.S. Pat. No. 3,185,704. The reaction product of anitrogen-containing dispersant and other suitable capping agents aredescribed in U.S. Pat. No. 4.663,064 (glycolic acid); U.S. Pat. Nos.4,612,132; 5,334,321; 5,356,552; 5,716,912; 5,849,676; 5,861,363 (alkyland alkylene carbonates, e.g., ethylene carbonate); U.S. Pat. No.5,328,622 (mono-epoxide); U.S. Pat. Nos. 5,026,495; 5,085,788;5,259,906; 5,407,591 (poly(e.g., bis)-epoxides) and U.S. Pat. No.4,686,054 (maleic anhydride or succinic anhydride). The foregoing listis not exhaustive and other methods of capping nitrogen-containingdispersants are known to those skilled in the art.

Oil of Lubricating Viscosity (A)

Oils of lubricating viscosity useful in the context of the presentinvention may be selected from natural lubricating oils, syntheticlubricating oils and mixtures thereof. The lubricating oil may range inviscosity from light distillate mineral oils to heavy lubricating oilssuch as gasoline engine oils, mineral lubricating oils and heavy dutydiesel oils. Generally, the viscosity of the oil ranges from 2 to 40,especially from 4 to 20, centistokes as measured at 100° C.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil); liquid petroleum oils and hydrorefined, solvent-treated oracid-treated mineral oils of the paraffinic, naphthenic and mixedparaffinic-naphthenic types. Oils of lubricating viscosity derived fromcoal or shale also serve as useful base oils.

Synthetic lubricating oils include hydrocarbon oils and halo-substitutedhydrocarbon oils such as polymerized and interpolymerized olefins (e.g.,polybutylenes, polypropylenes, propylene-isobutylene copolymers,chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes),poly(1-decenes)); alkylbenzenes (e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); andalkylated diphenyl ethers and alkylated diphenyl sulfides andderivative, analogs and homologs thereof. Also useful are synthetic oilsderived from a gas to liquid process from Fischer-Tropsch synthesizedhydrocarbons, which are commonly referred to as gas to liquid, or “GTL”base oils.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils. These are exemplified by polyoxyalkylene polymersprepared by polymerization of ethylene oxide or propylene oxide, and thealkyl and aryl ethers of polyoxyalkylene polymers (e.g.,methyl-polyiso-propylene glycol ether having a molecular weight of 1000or diphenyl ether of poly-ethylene glycol having a molecular weight of1000 to 1500); and mono- and polycarboxylic esters thereof, for example,the acetic acid esters, mixed C₃-C₈ fatty acid esters and C₁₃ oxo aciddiester of tetraethylene glycol.

Another suitable class of synthetic lubricating oils comprises theesters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkylsuccinic acids and alkenyl succinic acids, maleic acid, azelaic acid,suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with avariety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycolmonoether, propylene glycol). Specific examples of such esters includesdibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinoleic acid dimer, and the complex ester formed by reacting one moleof sebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol esters such as neopentylglycol, trimethylolpropane, pentaerythritol, dipentaerythritol andtripentaerythritol.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- orpolyaryloxysilicone oils and silicate oils comprise another useful classof synthetic lubricants; such oils include tetraethyl silicate,tetraisopropyl silicate, tetra-(2-ethylhexyl)silicate,tetra-(4-methyl-2-ethylhexyl)silicate,tetra-(p-tert-butyl-phenyl)silicate,hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl)siloxanes andpoly(methylphenyl)siloxanes. Other synthetic lubricating oils includeliquid esters of phosphorous-containing acids (e.g., tricresylphosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid)and polymeric tetrahydrofurans.

The oil of lubricating viscosity may comprise a Group I, Group II orGroup III, base stock or base oil blends of the aforementioned basestocks. Preferably, the oil of lubricating viscosity is a Group II orGroup III base stock, or a mixture thereof, or a mixture of a Group Ibase stock and one or more a Group II and Group III. Preferably, a majoramount of the oil of lubricating viscosity is a Group II, Group III,Group IV or Group V base stock, or a mixture thereof. The base stock, orbase stock blend, preferably has a saturate content of at least 65, morepreferably at least 75, such as at least 85%. Most preferably, the basestock, or base stock blend, has a saturate content of greater than 90%.Preferably, the oil or oil blend will have a sulfur content of less than1, preferably less than 0.6, most preferably less than 0.4% by weight.

Preferably the volatility of the oil or oil blend, as measured by theNoack volatility test (ASTM D5880), is less than or equal to 30%,preferably less than or equal to 25%, more preferably less than or equalto 20%, most preferably less than or equal 16%. Preferably, theviscosity index (VI) of the oil or oil blend is at least 85, preferablyat least 100, most preferably from about 105 to 140.

Definitions for the base stocks and base oils in this invention are thesame as those found in the American Petroleum Institute (API)publication “Engine Oil Licensing and Certification System”, IndustryServices Department, Fourteenth Edition, December 1996, Addendum 1,December 1998. Said publication categorizes base stocks as follows:

-   -   a) Group I base stocks contain less than 90 percent saturates        and/or greater than 0.03 percent sulfur and have a viscosity        index greater than or equal to 80 and less than 120 using the        test methods specified in Table I.    -   b) Group II base stocks contain greater than or equal to 90        percent saturates and less than or equal to 0.03 percent sulfur        and have a viscosity index greater than or equal to 80 and less        than 120 using the test methods specified in Table 1.    -   c) Group III base stocks contain greater than or equal to 90        percent saturates and less than or equal to 0.03 percent sulfur        and have a viscosity index greater than or equal to 120 using        the test methods specified in Table 1.    -   d) Group IV base stocks are polyalphaolefins (PAO).    -   e) Group V base stocks include all other base stocks not        included in Group I, II, III, or IV.

TABLE I Analytical Methods for Base Stock Property Test Method SaturatesASTM D 2007 Viscosity Index ASTM D 2270 Sulfur ASTM D 2622 ASTM D 4294ASTM D 4927 ASTM D 3120

(B) Additive Combination

As stated, the mass:mass ratio of (B1) to (B2) is in the range from 1:3to 9:1. Preferably it is in the range of 1:1 to 6:1 more preferably inthe range of 3:1 to 6:1. The respective masses are in terms of activeingredient.

The ratio of (B1) to (B2) may be expressed as the mass % of (B1), asactive ingredient, to the mass % of nitrogen in (B2). For example, inthese terms, it may be 30:1 to 750:1, such as 80:1 to 500:1, for example250:1 to 500:1; preferably, it is 40:1 to 80:1.

Also, as stated, additive combination (B) constitutes from 0.04 to 5mass % of the lubricating oil composition. Preferably, it constitutesfrom 0.2 to 2.5, more preferably from 0.4 to 2 mass %.

Also, the concentration of (B2) in the lubricating oil composition,expressed as the mass % of nitrogen, may be less than 0.03, such as lessthan 0.02, for example in the range of 0.002 to 0.01, such as in therange of 0.004 to 0.005 or to 0.01 mass %.

Co-Additives

The lubricating oil composition, to be useful in a trunk piston orcross-head diesel engine, will contain at least one overbased metaldetergent to provide the required TBN. Such detergents are well-knownand established in the art and examples include alkali metal or alkalineearth metal additives such as overbased oil-soluble or oil-dispersiblecalcium, magnesium, sodium or barium salts of a surfactants selectedfrom phenol, sulphonic acid, carboxylic acid, salicylic acid andnaphthenic acid, wherein the overbasing is provided by oil-insolublesalts of the metal, e.g., carbonate, basic carbonate, acetate, formate,hydroxide or oxalate, which is stabilized by the oil-soluble salt of thesurfactant. The metal of the oil-soluble surfactant salt may be the sameor different from that of the metal of the oil-insoluble salt.Preferably the metal, whether the metal of the oil-soluble salt oroil-insoluble salt, is calcium.

The TBN of the detergent may be low, i.e. less than 50, medium, i.e.50-150, or high, i.e. over 150. Preferably the TBN is medium or high,i.e. more than 50. More preferably, the TBN is at least 60, morepreferably at least 100, more preferably at least 150, and up to 500,such as up to 350.

Surfactants for the surfactant system of the overbased detergentpreferably contain at least one hydrocarbyl group, for example, as asubstituent on an aromatic ring. The term “hydrocarbyl” as used hereinmeans that the group concerned is primarily composed of hydrogen andcarbon atoms and is bonded to the remainder of the molecule via a carbonatom but does not exclude the presence of other atoms or groups in aproportion insufficient to detract from the substantially hydrocarboncharacteristics of the group. Advantageously, hydrocarbyl groups insurfactants for use in accordance with the invention are aliphaticgroups, preferably alkyl or alkylene groups, especially alkyl groups,which may be linear or branched. The total number of carbon atoms in thesurfactants should be at least sufficient to impart the desiredoil-solubility.

Other co-additives that may be used include for example:

Anti-wear additives such as metal (e.g. Zn) salts of dihydrocarbyldithiophosphates (e.g. in an amount of from 0.10 to 3.0 mass % of thelubricating oil composition); anti-oxidants, or oxidation inhibitors,for example in the form of aromatic amines or hindered phenols (e.g. inan amount of up to 3 mass % of the lubricating oil composition);

Other additives such as pour point depressants, anti-foamants, metalrust inhibitors, pour point depressants and/or demulsifiers may beprovided, if necessary.

The terms ‘oil-soluble’ or ‘oil-dispersable’ as used herein do notnecessarily indicate that the compounds or additives are soluble,dissolvable, miscible or capable of being suspended in the oil in allproportions. These do mean, however, that they are, for instance,soluble or stably dispersible in oil to an extent sufficient to exerttheir intended effect in the environment in which the oil is employed.Moreover, the additional incorporation of other additives may alsopermit incorporation of higher levels of a particular additive, ifdesired.

The lubricant compositions of this invention comprise defined individual(i.e. separate) components that may or may not remain the samechemically before and after mixing.

It may be desirable, although not essential, to prepare one or moreadditive packages or concentrates comprising the additives, whereby theadditives can be added simultaneously to the oil of lubricatingviscosity to form the lubricating oil composition. Dissolution of theadditive package(s) into the lubricating oil may be facilitated bysolvents and by mixing accompanied with mild heating, but this is notessential. The additive package(s) will typically be formulated tocontain the additive(s) in proper amounts to provide the desiredconcentration, and/or to carry out the intended function in the finalformulation when the additive package(s) is/are combined with apredetermined amount of base lubricant.

Thus, the additives may be admixed with small amounts of base oil orother compatible solvents together with other desirable additives toform additive packages containing active ingredients in an amount, basedoil the additive package, of, for example, from 2.5 to 90, preferablyfrom 5 to 75, most preferably from 8 to 60 mass % of additives in theappropriate proportions, the remainder being base oil.

EXAMPLES

This invention will now be described in the following examples which arenot intended to limit the scope of the claims hereof.

Synthesis Synthesis Example 1

Preparation of a compound of Formula (II):

Step 1—Preparation of 2-(2-naphthyloxy)ethanol

A two-liter resin kettle equipped with mechanical stirrer,condenser/Dean-Stark trap, and inlets for nitrogen, was charged with2-naphthol (600 g, 4.16 moles), ethylene carbonate (372 g, 4.22 moles)and xylene (200 g), and the mixture was heated to 90° C. under nitrogen.Aqueous sodium hydroxide (50 mass %, 3.0 g) was added and water wasremoved by azeotropic distillation at 165° C. The reaction mixture waskept at 165° C. for 2 hours. CO₂ evolved as the reaction progressed andthe reaction was determined to be near completion when the evolution ofCO₂ ceased. The product was collected and solidified while cooling toroom temperature. The completion of reaction was confirmed by FT-IR andHPLC. The structure of the 2-(2-naphthyloxy)ethanol product wasconfirmed by 1H and ¹³C-NMR.

Step 2—Oligomerization of 2-(2-naphthyloxy)ethanol

A two-liter resin kettle equipped with mechanical stirrer,condenser/Dean-Stark trap, and inlets for nitrogen, was charged with2-(2-naphthyloxy)ethanol from Step 1, toluene (200 g), SA 117 (60.0 g),and the mixture was heated to 70° C. under nitrogen. Para-formaldehydewas added over 15 min at 70-80° C., and heated to 90° C. and thereaction mixture was kept at that temperature for 30 min to 1 hour. Thetemperature was gradually increased to 110° C. to 120° C. over 2-3 hoursand water (75-83 ml) was removed by azeotropic distillation. The polymerwas collected and solidified while cooling to room temperature. M _(n)was determined by GPC using polystyrene standard corrected with theelution volume of 2-(2-naphthyloxy)ethanol as internal standard. THF wasused as eluent, ( M _(n) of 1000 dalton). ¹H and ¹³C NMR confirmed thestructure. FDMS and MALDI-TOF indicates the product contains mixture ofmethylene-linked 2-(2-naphthyloxy)ethanol oligomer of Formula (I)containing from 2 to 24 2-(2-naphthyloxy)ethanol units (m is 1 to 23).

Step 3—Reaction of Methylene-Linked 2-(2-naphthyloxy)ethanol oligomerand an Acylating Agent (PIBSA)

A five-liter resin kettle equipped with mechanical stirrer,condenser/Dean-Stark trap, inlets for nitrogen, and additional funnelwas charged with poly(2-(2-naphthyloxy)ethanol)-co-formaldehyde) fromStep 2, toluene (200 g), and the mixture is heated to 120° C. undernitrogen. Polyisobutenyl succinic anhydride (PIBSA M _(n) of 450, 2,500g) was added portion wise (˜250 g at 30 min intervals) and thetemperature was maintained at 120° C. for 2 hours followed by heating to140° C. under nitrogen purge for an additional 2 hours to strip off allsolvents to a constant weight. Base oil (AMEXOM 100 N, 1100 g) wasadded, and the product was collected at room temperature. GPC and FT-IRconfirmed the desired structure.

The reaction scheme representing the above synthesis is shown below:

Testing and Results

The following examples use a centrifuge water shedding test whichevaluates the ability of an oil to shed water from a prepared testmixture of oil and water. The test uses an Alfa Laval MAB103B 2.0centrifuge coupled to a Watson Marlow peristaltic pump. The centrifugeis sealed with 800 ml of water. A measurement is made of the amount ofdeposits formed in the centrifuge during the test. Pre-measured amountsof water and the test oil are mixed together and then passed through thecentrifuge at a rate of 2 litres/min. The test is run for an hour and ahalf, allowing the mixture to pass through the centrifuge about 10times. The centrifuge is weighed before and after the test. A poor trunkpiston diesel engine lubricant will produce a larger amount of depositsin the centrifuge system.

A set of lubricant formulations was tested as set forth in the tablebelow. Reference Examples A, B and C are for comparison purposes.Example 1 is an example of the invention. The key to the table is asfollows:

PIBSA/PAM: a polyisobutenyl succinic anhydride/polyamine dispersant.PmNE: the final product of Synthesis Example 1 above.

Each formulation comprised a Group II base oil and a Group I brightstock, a zinc dihydrocarbyl dithiophosphate antiwear additive, and adetergent system in the form of a 225 TBN calcium salicylate and a 350TBN calcium salicylate in the ratio (mass:mass) of 1.419:1.Additionally, each formulation contained one or both of a PIBSA/PAM andthe PmNE in the amounts (mass %) given in the table below; otherwise theformulations are equivalent.

PmNE (active PIBSA/PAM TOTAL MASS OF EXAMPLE ingredient) (mass % N)DEPOSITS MEASURED (g) Reference A 0.012* 140 Reference B 0.4 — 72Reference C — 0.00426** 35 1 0.32 0.00426** 45 *corresponds to 0.6 mass% active ingredient **corresponds to 0.1 mass % active ingredient

Reference Example C contains a low total proportion of dispersant andtherefore exhibits a good water shedding result as demonstrated by thelow mass of deposits. Reference Example C, however, would exhibit poorsoot handling properties because of its low total proportion ofdispersant.

Reference Examples A and B, respectively containing PIBSA/PAM and PmNEas sole dispersants and, for Reference Example A, in a higher proportionthan in Reference Example C, exhibit poor water shedding properties.

Example 1, of the invention, contains both PIBSA/PAM and PmNE andexhibits much better water shedding performance than Reference ExamplesA and B at the same total dispersant treat rate. Also, because of itshigher total dispersant treat rate, Example 1 would exhibit much bettersoot handling properties than Reference Example C.

1. A method of lubricating a trunk piston or cross-head diesel enginehaving a centrifuge system including a sealing medium comprisingoperation of the engine and lubrication of the trunk piston engine orsystem lubrication of the cross-head engine with a lubricating oilcomposition comprising, or made by admixing: (A) an oil of lubricatingviscosity, in a major amount; and (B) from 0.04 to 5 mass %, expressedas active ingredient, of the lubricating oil of a combination of: (B1)at least one linked aromatic compound of the formula:

wherein: each Ar independently represents an aromatic moiety having 0 to3 substituents selected from the group consisting of alkyl, alkoxy,alkoxyalkyl, hydroxy, hydroxyalkyl, acyloxy, acyloxyalkyl, aryloxy,aryloxy alkyl, halo and combinations thereof; each L is independently alinking moiety comprising a carbon-carbon single bond or a linkinggroup; each Y′ is independently a moiety of the formulaZ(O(CR₂)_(n))_(y)X—, wherein X is selected from the group consisting of(CR′₂)_(z), O and S; R and R′ are each independently selected from H, C₁to C₆ alkyl and aryl; z is 1 to 10; n is 0 to 10 when X is (CR′₂)_(z),and 2 to 10 when X is O or S; y is 1 to 30; Z is H, an acyl group, analkyl group or aryl group; each a is independently 0 to 3, with theproviso that at least one Ar moiety bears at least one group Y′ in whichZ is not H; and m is 1 to 100, and (B2) at least one nitrogen-containingdispersant, where the mass:mass ratio of (B1) to (B2) is in the ragefrom 1:3 to 9:1.
 2. A method as claimed in claim 1, wherein saidmass:mass ratio of (B1) to (B2) is in the range of from 1:1 to 6:1.
 3. Amethod as claimed in claim 2, wherein said mass:mass ratio of (B1) to(B2) is in the range of from 3:1 to 6:1.
 4. A method as claimed in claim1, wherein Y′ is Z(O(CR₂)₂)yO—, Z is an acyl group and y is 1 to
 6. 5. Amethod as claimed in claim 4, wherein Ar is naphthalene, Y′ isZOCH₂CH₂O—, Z is an acyl group and L is CH₂.
 6. A method as claimed inclaim 5, wherein Ar is derived from 2-(2-naphthyloxy)-ethanol and m is 2to
 25. 7. A method as claimed in claim 6, wherein Z is derived from apolyalkyl or polyalkenyl succinic acylating agent having M _(n) of fromabout 100 to about
 5000. 8. A method as claimed in claim 6, wherein Z isderived from hydrocarbyl isocyanate.
 9. A method as claimed in claim 1,wherein the nitrogen-containing dispersant is a polybutenylpolyalkyleneamine succinimide derived from polybutene having an M _(n)of from 900 to
 2500. 10. A method as claimed in claim 1, wherein thelubricating oil composition comprises one or more overbased calciumsalicylate detergent additives and has a total base number of at least15 mg KOH/g, as determined by ASTM D2896.
 11. A method as claimed inclaim 1, wherein the sealing medium is water.
 12. A method of enhancingthe water-shedding properties, as measured by a centrifuge watershedding test, of a lubricating oil composition in the lubrication of atrunk piston engine or the system lubrication of cross-head dieselengine by employing a lubricating oil composition as defined in claim 1when compared with a corresponding lubricating oil composition where (B)contains only (B2).
 13. A method as claimed in claim 12, wherein thesealing medium is water.
 14. A trunk piston or cross-head diesel enginelubricating oil composition having a total base number of at least 15 mgKOH/g, as determined by ASTM D2896, comprising: (A) at least 40 mass %of an oil lubricating viscosity; and (B) from 0.04 to 5 mass %,expressed as active ingredient, of the lubricating oil of a combinationof: (B1) at least one linked aromatic compound of the formula:

wherein: each Ar independently represents an aromatic moiety having 0 to3 substituents selected from the group consisting of alkyl, alkoxy,alkoxyalkyl, hydroxy, hydroxyalkyl, acyloxy, acyloxyalkyl, aryloxy,aryloxy alkyl, halo and combinations thereof; each L is independently alinking moiety comprising a carbon-carbon single bond or a linkinggroup; each Y′ is independently a moiety of the formulaZ(O(CR₂)_(n))_(y)X—, wherein X is selected from the group consisting of(CR′₂)_(z), O and S; R and R′ are each independently selected from H, C₁to C₆ alkyl and aryl; z is 1 to 10; n is 0 to 10 when X is (CR′₂)_(z),and 2 to 10 when X is O or S; y is 1 to 30; Z is H, an acyl group, analkyl group or an aryl group; each a is independently 0 to 3, with theproviso that at least one Ar moiety bears at least one group Y′ in whichZ is not H; and m is 1 to 100, and (B2) at least one nitrogen-containingdispersant, where the mass:mass ratio of (B1) to (B2) is in the rangefrom 1:3 to 9:1.
 15. The lubricating oil composition as claimed in claim14, wherein said mass:mass ratio of (B1) to (B2) is in the range from1:1 to 6:1.
 16. The lubricating oil composition as claimed in claim 15,wherein said mass:mass ratio of (B1) to (B2) is in the range from 3:1 to6:1.
 17. The lubricating oil composition as claimed in claim 14, whereinY′ is Z(O(CR₂)₂)yO—, Z is an acyl group and y is 1 to
 6. 18. Thelubricating oil composition as claimed in claim 17, wherein Ar isnaphthalene, Y′ is ZOCH₂CH₂O—, Z is an acyl group and L is CH₂.
 19. Thelubricating oil composition as claimed in claim 18, wherein Ar isderived from 2-(2-naphthyloxy)-ethanol and m is 2 to
 25. 20. Thelubricating oil composition as claimed in claim 19, wherein Z is derivedfrom a polyalkyl or polyalkenyl succinic acylating agent having M _(n)of from about 100 to about
 5000. 21. The lubricating oil composition asclaimed in claim 19, wherein Z is derived from hydrocarbyl isocyanate.22. The lubricating oil composition as claimed in claim 14, wherein thenitrogen-containing dispersant is a polybutenyl polyalkyleneaminesuccinimide derived from polybutene having an M _(n) of from 900 to2500.
 23. The lubricating oil composition as claimed in claim 14,further comprising one or more overbased calcium salicylate detergentadditives.
 24. The lubricating oil composition as claimed in claim 14,having a total base number of at least 20 mg KOH/g, as determined byASTM D2896.